Motor fuel



7 tion.

United States Patent Gee MOTOR FUEL Troy L. Cantrell, Drexel Hill, Pa.,and John G. Peters, Audubon, N. J., assignors to Gulf Oil Corporation,Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. ApplicationOctober 4, 1954 Serial No. 460,237

4 Claims. (Cl. 44-69) This invention relates to fuels and moreparticularly to leaded gasolines for high compression, spark ignitionengines.

It has long been recognized that for greater economy with respect tofuel requirement and greater efiiciency in the operation of a gasolineengine high compression ratios are desired. As a result, severalautomobile manufacturers have increased the compression ratios of theirspark ignition engines to 8.5 to 1 and even as high as 9 to 1, thefuture trend of the automotive industry indicating that substantiallyall engines will be operating at such high compression ratios in theforeseeable future. In order to obtain smooth engine operation at thesehigh compression ratios, it has been necessary to employ a fuel having ahigh octane number. To obtain a high octane number most fuels requirethe addition of an anti: knock agent such as tetraethyl lead. While theaddition of tetraethyl lead to gasoline improves its octane numher, theresulting fuel has certain disadvantages arising from the presence ofthe lead. One of the chief objections to the use of leaded gasolinesarises from the tendency of the fuel upon being burned to formdecomposition products of lead which products are deposited on the wallsof the combustion chambers of the engine and on the electrodes andinsulators of the spark plugs, thus reducing the efliciency of theengine and olfsetting to some extent the increased efficiency obtainedby the high compression ratios. The net effect of these deposits is thatthe octane number requirement of the engine gradually increases as theengine is operated until some equilibrium octane number requirement isreached. The equilibrium octane number requirement of some engines whichhave been in operation for 100 or more hours may be 10 to numbers higherthan the octane number requirement of the same engines at the start oftheiropera-- In an attempt to overcome the detrimental effect of thedeposits of lead decomposition products in an engine, various scavengingagents have been added to the fuel to change the form of the leaddecomposition products ,to those which are more volatile and thus lesslikely to be deposited within the engine. For example, various volatilealkyl halides such as ethylene dibromide and/or ethylene dichloride havebeen used with tetraethyl lead to produce the corresponding halides oflead which are more volatile than the oxides. The volatile alkylhalides, however, have not completely overcome the deposition of thedecomposition products. The decomposition products comprise varioussalts including the oxides, sulfates, bromides and chlorides of lead.These decomposition salts deposited within the combustion chamber of theengine have been found to alter adversely the ignition characteristics.The adverse effect encountered as a result of the deposits of thedecomposition salts is frequently evidenced by engine knocking. Theknocking thus encountered is that associated with preignition of thefuel in the combustion chamber of a spark ignition engine. This knockingassociated with preignition 2,863,744 Patented Dec. 9, 1958 should notbe confused with knocking" due to explosive autoignition of the unburnedportion of the fuel-air mixture to be traversed by the normal flame fromthe spark plug.

We have discovered that a motor fuel, and particularly a gasoline towhich a mixture consisting of tetraethyl lead and an ethylene halide hasbeen added in an amount suficient to produce a leaded fuel having aresearch octane number of at least 90, can be improved with respect toits tendency to preignite in an engine by incorporating in said gasolinea small amount of the cyclohexylamine salt of 3-methylbutyl,2-ethylhexyl acid orthophosphate.

The cyclohexylamine salt of 3-methylbutyl,Z-ethylhexyl acidorthophosphate is oil soluble and is a relatively stable compound underordinary conditions of temperature and pressure. However, if thecompound is heated to excessive temperatures, in the order of 260 F. orabove, for long periods, it is converted into the corresponding amidecompound, water being split off at such high temperatures. However, attemperatures below said conversion temperature, it is a relativelynon-volatile material. At such elevated temperatures, it is an oilyliquid, being rather viscous at room temperature. Upon prolongedstanding at room temperature it becomes more or less crystalline, itbeing definitely crystalline at lower tempreatures. This salt isinsoluble in water and aqueous liquids, and is resistant to hydrolysis.It can be readily prepared by reacting isoamyl octyl acid'phosphate withcyclohexylamine in approximately equimolecular proportions, the reactionbeing so controlled as to produce substantially neutral reactionmixtures having a pH value within the range of 5.5 to 7.5. The isoamyloctyl acid phosphate employed is a di-ester of orthophosphoric acid Hhaving the following formula:

hexyl acid orthophosphate.

The reaction between the cyclohexylamine and the isoamyl octyl acidphosphate is quite exothermic, thus requiring cooling means to maintainthe reaction temperature Within the desired limits. The temperature isadvantageously maintained between and 180 F.

The amountof the cyclohexylamine salt of .B-methylbutyl,2-ethylhexylacid orthophosphate which is incorporated in the fuel depends upon theamount of tetraethyl lead in the fuel. In general, the amount is basedupon that amount theoretically required to convert the lead introducedinto the fuel in the form of tetraethyl lead to lead orthophosphate.Good results are obtained by using at least 0.3 times the theoreticalamount required. In general, it is not necessary to employ more than 1.5times the amount theoretically required. Amounts greater than 1.5 timesthe theoretical amount can be employed, but for economic reasons, weprefer to use only the amount required to give the desired improvement.When less than 0.3 times the theoretical amount is used the preignitioncharacteristic of the leaded gasoline in engines having compressionratios in the order of 9 to 1 is not substantially improved. Thetheoretical amount of the cyclohexylamine salt of3-methylbutyl,2-ethylhexyl acid orthophosphate required to convert thelead in tetraethyl lead to lead orthophosphate on a molecular proportionbasis is two mols of the cyclohexylamine salt to threemols of tetraethyllead.

In view of the fact that the amount of tetraethyl lead in the gasolinevaries from one fuel to another, it is difficult to state on a weightbasis theamount of the cyclohexylamine salt of3-methylbutyl,2-ethylhexyl acid orthophosphate based upon the weight ofgasoline. However, once knowing the amount of tetraethyl lead present inthe gasoline the amount of the cyclohexylamine salt of3-methylbutyl,2-ethylhexyl acid orthophosphate required can be readilycalculated. Based uponfuels containing three cubic centimeters oftetraethyl lead per gallon of gasoline, we have determined that theamount of the cyclohexylamine salt'of 3-methylbutyl,2-ethylhexyl acidorthophosphate required in accordance with our invention is between0.045 and 0.225 percent by weight based on the weight of a 60 API gravitgasoline. It will be understood of course that when commerciallyavailable products are used the optimum amount of product on a weightbasis will vary depending upon the purity of the product. If, forinstance, a commercially available anti-knock mixture comprisingtetraethyl lead and ethylene halides is used, the percent by weight ofthe cyclohexylamine salt will be less than if substantially puretetraethyl lead is used. vFor example, if three cubic centimeters of atetraethyl lead mixture comprising 61.5 percent by weight of tetraethyllead is used, the amount of the cyclohexylamine salt required in onegallon of a 60 API gravity gasoline to give between 0.3 and 1.5 theoriesis between about 0.027 and about 0.138 percent by weight. Acyclohexylamine material consisting of about 25 percent by weight of thecyclohexylamine salt of 3-methylbutyl,2-ethylhexyl acid orthophosphatewill be used in greater proportions than the pure product. In order toincorporate between 0.045 and 0.225 percent by weight of thecyclohexylamine salt of 3-methylbutyl,2-ethylhexyl acid orthophosphatein gasoline when using the 25 percent concentrate, it would be necessaryto employ between about 0.18 and about 0.9 percent by weight of theconcentrate. Since the above weight percents are based upon three cubiccentimeters of tetraethyl lead, the percents will vary directly with thelead content as more or less than three cubic centimeters of tetraethyllead are employed. In any event, the amount of the cyclohexylamine saltof 3-methylbutyl,- 2-ethylhexyl acid orthophosphate used is sutficientto inhibit or substantially prevent preignition of a gasoline containingtetraethyl lead and an ethylene halide in an amount normally tending tocause preignition of the gasoline in the combustion chamber of anengine.

The motor fuel to which the cyclohexylamine salt of3-methylbutyl,2-ethylhexyl acid orthophosphate is added can comprise amixture of hydrocarbons boiling in the gasoline boiling range. However,the problem of preignition is primarily present in heavily leadedgasolines having a research octane number of at least about 90. Thegasoline to which the tetraethyl lead is added can be either astraight-run gasoline or a gasoline obtained froma conventional crackingprocess, or mixtures thereof. The gasoline to which the cyclohexylaminesalt of 3-methylbutyl,2-ethylhexyl acid orthophosphate is added inaccordance with our invention can also contain components obtained fromprocesses other than cracking, such as alkylation,isomerization,hydrogenation, polymerization, hydrodesulfurization,hydroforming, Platforming, or combinations of two .or more of suchprocesses, as well as synthetic gasoline obtained from the Fischer-Tropsch and related processes.

In addition to the cyclohexylamine salt of 3-methylbutyl,2-et hylhexylacid orthophosphate, the leaded gasoline of our invention can containother conventional additive agents including upper cylinder lubricants,oxidation inhibitors, anti-freeze agents, metal deactivators, dyes, andthe like. 6

The cyclohexylamine salt of 3-methylbutyl,2-ethylhexyl acidorthophosphate presents no particular problem with respect to itsaddition to gasoline. While the cyclohexylamine salt can be addeddirectly to the gasoline, oneconvenient method of adding it to the fuelis to form a concentrate thereof with a liquid hydrocarbon solvent andthereafter adding the concentrate to the fuel. Any

r.- solvent which does not adversely affect the desirable properties ofthe fuel can be used. One concentrate which We have found suitable forthe purpose of our invention consists of about 25 percent by weight ofthe cyclo hexylamine salt of 3-methylbutyl, 2-ethylhexyl acidorthophosphate and 75 percent by weight of toluene. The concentrate can,of course, contain other conventional gasoline additives, if desired.

Thus, a gasoline-benefiting concentrate can be formed by admixing anorgano-metallic anti-knock composition with the cyclohexylamine salt of3-methylbutyl,2-ethylhexyl acid orthophosphate. In such instances, amutual solvent may be desirable. When such gasoline-benefitingconcentrates are prepared, they can, of course, contain other additiveagents such as an oxidation inhibitor, an anti-freeze agent, a metaldeactivator, an upper cylinder lubricant, a lead scavenging agent, a dyeand the like. Since the amount of the cyclohexylamine salt of3-methylbutyl,2-ethylhexyl acid orthophosphate depends upon the amountof the tetraethyl lead present, this method of adding thecyclohexylamine salt to the gasoline servesas a convenient way of addingthe correct amount of cyclohexylamine salt to unleaded gasolines. Thus,a gasoline-benefiting concentrate can be made by admixing tetraethyllead with the cyclohexylamine salt of 3-methylbutyl,Z-ethylhexyl acidorthophosphate. Such concentrates advantageously contain volatile alkylhalides. Thus, a gasoline-benefiting concentrate can be made by admixingtetraethyl lead and a halide of ethylene with the cyclohexylamine saltof 3-methylbutyl,2-ethylhexyl acid orthophosphate wherein thecyclohexylamine salt is present in an amount between 0.3 and. 1.5 timesthetheoretical amount required to convert the lead to lead phosphate. pp

The proportions of the constituents in such a gasoline: benefitingconcentrate may vary depending upon the characteristics of the basegasoline as Well as the compression ratio of the engine in which thegasoline is to be used. Good results can be obtained, however, with acomposition consisting of about 35 to about 55 percent by weight oftetraethyl lead, about 20 to about 35 percent by weight of a mixture ofethylene halides and about 10 to about 45 percent by weight of thecyclohexylamine salt of 3-methylbutyl,2-ethylhexyl acid orthophosphate,the cyclohexylamine salt being present in at least 0.3 times thetheoretical amount required to convert the lead in the tetraethyl leadto lead phosphate.

One convenient method of preparing a gasoline-benefiting concentrate isto start with a commercially available concentrate comprising tetraethyllead and the halides of ethylene.v One such commercially availableproduct consists of about 61.5 percent by weight of tetraethyl lead,about 17.9 percent by weight of ethylene dibromide and about 18.8percent by weight of ethylene dichloride. This commercially availableconcentrate has .a specific gravity of 1.587 at 20 C. The amount of thegasoline-benefiting concentrate added to gasoline .will vary dependingupon the octane number of the gasoline desired. Ordinarily theconcentrate is added in an amount sufficient to incorporate betweenabout one and about three cubic centimeters of tetraethyl lead in agallon of gasoline. p I

In order to illustrate the improvedpreignition'characteristic's obtainedwith'ajfuel of' the'invention, a'test was employed in which the'fuel wasburned in a stationary Cadillac engine having a9 to 1 compression ratio.In this test, theengine was operated on a cycling schedule consisting ofthree minutes at 1500 R P. M., road loa'd followed by a one-minute idleat 450 RP. M. At the end of each twenty-four hours under this cyclingsched- -ule,.prei'gnition determinations were made at 1000and 2000 R. P.M. After the preignition determinations were made the engine was thenput back on'the cycling schedtile. The test was continued untilviolentpreignition was encountered for two; successive periods,regardless of whether such preignition occurred at 1000 or 2000 R. P. M.The engine conditions at the time of the preignition evaluation were asfollows:

Speed 1000 and 2000 R. P. M. Spark advance Air:fuel ratio 11.521 and10.3:1 at

1000 and 2000 R. P. M., respectively.

In this test the load and throttle position are varied, dependent uponwhen preignition is encountered. At the start of the test the engine isunder no load. The throttle is gradually increased until preignition isobserved. If full throttle is reached without preignition, the engine isoperated at full throttle for 30 seconds, or less if preignition occurssooner. If preignition is not encountered after 120 hours (5 days), thetest is usually discontinued. The data set forth in Table I was obtainedwhen the Cadillac engine was operated under the above test procedurewith a reference gasoline, normally tending to preignite, containingabout 2.0 cubic centimeters (3.32 grams) of tetraethyl lead and about1.98 grams of about a 50-50 mixture of ethylene dibromide and ethylenedichloride per gallon of gasoline. The comparative test was made withthe same base gasoline containing 0.78 gram (0.3 times the theory) ofthe cyclohexylamine salt of 3-methylbutyl,2-ethylhexyl acidorthophosphate per gallon of gasoline. This quantity of thecyclohexylamine salt was incorporated in the gasoline in the form of aconcentrate consisting of 25 percent by weight of the cyclohexylaminesalt and 75 percent by weight of toluene. The concentrate was added inan amount corresponding to 0.106 percent by weight based on the WithReference Gasoline Ccntaining 0.78 Gram (0.3 Times the Theory) of theCyclohexylamine Salt of 3- methylbutyl,2-ethylhexyl acid orthophosphateat- Wlth Reference Gaso- Hours of Operation line at- 2,000 B. P. M.

It will be noted from the data in Table I that the engine operating withthe reference gasoline went into violent preignition within 48 hours.This preignition was sustained as determined after cycling was continuedfor another 24 hours. Since sustained violent preignition occurredwithin 72 hours, the engine was not operated past the 72-hour period.When the same engine was operated with the reference gasoline containing0.3 times the theory of the cyclohexylamine salt of3-methylbutyl,2-ethylhexyl acid orthophosphate, there was no violentpreignition even after hours of operation. Thus, it can be seen that thenormal tendency of the reference gasoline to preignite was overcome bythe addition of 0.3 times the theory of the cyclohexylamine salt of3-methylbutyl,2-ethylhexyl acid orthophosphate.

While our invention is described above with reference to variousspecific examples and embodiments, it will be understood that theinvention is not limited to such examples and embodiments and may bevariously practiced within the scope of the claims hereinafter made.

We claim:

1. A motor fuel consisting essentially of a gasoline containingtetraethyl lead and an ethylene halide in an amount normally tending tocause preignition of said gasoline in the combustion chamber of a sparkignition engine and at least 0.3 times the theoretical amount requiredto convert the lead to lead phosphate of the cyclohexylamine salt of3-methylbutyl,2-ethy1hexyl acid ortho' phosphate.

2. A motor fuel consisting essentially of a gasoline containingtetraethyl lead and an ethylene halide in an amount normally tending tocause preignition of said gasoline in the combustion chamber of a sparkignition engine, said fuel containing between 0.3 to 1.5 times thetheoretical amount required to convert the lead to lead phosphate of thecyclohexylamine salt of 3-methylbutyl,- 2-ethylhexyl acidorthophosphate.

3. A gasoline-benefiting concentrate consisting essentially oftetraethyl lead containing the cyelohexylamine salt of3-methylbutyl,2-ethylhexyl acid orthophosphate in an amount betweenabout 0.3 and 1.5 times the theoretical amount required to convert thelead to lead phosphate.

4. A gasoline-benefiting concentrate consisting of about 35 to about 55percent by weight of tetraethyl lead, about 20 to about 35 percent byweight of a mixture of ethylene halides and about 10 to about 45 percentby weight of the cyclohexylamine salt of 3-methylbutyl,2-ethylhexyl acidorthophosphate, the cyclohexylamine salt being present in at least 0.3times the theoretical amount required to convert the lead in saidtetraethyl lead to lead phosphate.

References Cited in the file of this patent UNITED STATES PATENTS2,296,200 Cantrell et a1 Sept. 15, 1942 2,297,114 Thompson Sept. 29,1942 2,301,370 Cook et al Nov. 10, 1942 2,371,852 Smith et a1. Mar. 20,1945 2,405,560 Campbell Aug. 13, 1946 2,728,645 Vaughn Dec. 27, 1955FOREIGN PATENTS 600,191 Great Britain Apr. 2, 1948 1,043,087 France June10, 1953

1. A MOTOR FUEL CONSISTING ESSENTIALLY OF A GASOLINE CONTAININGTETRAETHYL LEAD AND AN ETHYLENE HALIDE IN AN AMOUNT NORMALLY TENDING TOCAUSE PREIGNITION OF SAID GASOLINE IN THE COMBUSTION CHAMBER OF A SPARKIGNITION ENGINE AND AT LEAST 0.3 TIMES THE THEORETICAL AMOUNT REQUIREDTO CONVERT THE LEAD TO LEAD PHOSPHATE OF THE CYCLOHEXYLAMINE SALT OF3-METHYLBUTYL,2-ETHYLHEXYL ACID ORTHOPHOSPHATE.